Furnace bridge wall



June 15, 1937.

A. HYND FURNACEBMDGE WALL Filed Aug. 17, 1954 e Z641' 16a( 165:'

m M n I-I-I Patented June 15, 1937 'r orrics Application August 17,

'7 Claims.

This invention relates to combustion furnaces and the like, and more particularly to an improved form of furnace bridge Walls for such furnaces, the bridge wall being that part of the furnace structure commonly found at the rearmost end of the grate. separating the fire box from the combustion chamber.

Heretofore, bridge walls for such application have been constructed of fire brick, metal, and other materials, and have been arranged in many different forms to provide for a proper distribution of secondary air for the purposes of combustion. However, the prior forms of bridge Wall structure have all had certain highly undesirable '15 disadvantages, among. others, a tendency to burn out-especially in and about their rear and uppermost (bridge) ends, due to the concentration of hot gases and corresponding lack of cooling air about these regions. o A further disadvantage with other forms of bridge wall has been the diiiiculty encountered in removing for replacement or repair one or more of the several bars comprising the wall, it being commonly necessary to remove a large number of the entire set in order to remove a particular bar. Still another disadvantage of the old types of wall structure lies in the danger of displacing the bridge bars of a set by the accidental insertion of stoking andV scavenging tools between the bars, and especiallyr between the grate and the lower or foot end of the bars.

An important object of the present invention is the provision. of an improved form of bridge wall, the bars of which have certain conformations particularly designed to direct the movement of air in several paths for both combustion and cooling purposes.

Another object is the provision of improved mounting means or bearer plates for the individual bars of the bridge Wall.

Another object is the provision of bridge Wall bars having conformations and recesses particularly adapted to direct cooling air against the uppermost or trailingends of the bars forming the bridge.

A further object of the invention is the provision of bridge wall bars having conformations and mounting appendages adapted to prevent accidental dislodgement of the bars by firing and stoking tools working over the grate.

Yet another object is the provision of bridge bars and mounting means therefor so designed that individual bars may be readily removed without disturbing the other bars of the set.

Still other objects of this invention relate to the 1934, Serial No. 740,311

provision of improved bridge bars and mounting means therefor whereby proper distribution of fuel and cooling air, together with economy of fuel consumption, reduction of smoke, simplicity of construction, durability, shortened length of grate, and absence of clinker adherence to the bridge bars are all obtained as distinct advantages of the improved structures herein set forth and particularly described.

The illustrations and description herein show the application ofI my invention to internally red boilers of the type known as Scotch boilers, but it is to be understood that the invention is not restricted to anyA particular type of boiler, and may be applied to the so-called Dutch furnace or any other furnace of this general class and type.

In the accompanying drawing:

Fig. 1 is a longitudinal view, partly ink section, of my bridge wall structure showing the grate, the bearer or mounting plates, the bridge barfs) right side, and the relation ofthe fuel bed to these parts,

Fig. 2 is similar to Fig. 1 and shows ythe opposite (left) side of the bridge wall plate or bar shown in Fig. 1,

Fig. 3 is a partial front elevation of the lbridge wall partly in section taken along the line 3-3 of Fig. 1,

Fig. 4 is a detail sectional View of the back bearer plate taken along the line 1 -4v of Fig- 2, and

Fig. 5 is a detail sectional View of the bridge wall barstaken along the line 5-5 of Fig. 2.

The complete bridge assembly as shown in Fig. 1 comprises generally a main bearer plate l0 to which is attached a back bearer plate-8, and the ash pit closing plate l2. The front part of the main bearer plate forming a receptacle or receiving channel for the lowermost or foot part ofthe bridge wall assembly (I6) and the rear end of the bars which form the grate M. The upper ends of the bridge wall assemblyV or bars resting preferably by means of slotted engagement on and with the back bearer plate 8, as at the point 3|.

It will be observed from Figs. 1, 2, and 3 that the bridge bars IS are of peculiar shape, having their opposite faces la and lh differently formed with particular respect to their marginal flanges and 26 and the indentures or slots 20, 20 and 29 therein, in such manner that when the bars are assembled side by side as in Fig; 3, they form alternate units or pairs, such as itc-ltd, having forward and rearward air passages and vents 29,20' and 24 (Figs. 3, 4)V ad.-

mitting air through (i. e., from back to front) the bridge wall, between the plates or bars, and into the fire bed; and other alternate units or pairs such as Nid-16e (Fig. 3) admitting air 5 only to the combustion chamber at a point adjacent or beyond the rear bearer 8 by a path inside of the bridge plates, that is-interiorally of the bridge wall proper.

Thus, with respect to their opposing or con- 10 fronting faces, the bars are designated as right and left hand, and in their assembled relation the confrontation of right and left-hand faces forms alternate units or pairs resulting in the openings or passages or channels for air which l5 are substantially independent. l

These individual bars IS are generally elongated, flat, metal plates, somewhat in the shape of a hook, though not necessarily of such configuration so far as the direction of air is con cerned. For convenience in description, the long, lengthwise edges or boundaries or margins of these bridge plates or bars are referred to herein as the longitudinal edges or margins, the back or rear longitudinal edge being that nearest the back bearer plate 8, and the front or forward longitudinal edge being that nearest the grate I4 or the fire bed, as seen in Fig. 1.

'I'he lower, relatively narrow lateral edge of these plates which rests on the bearer ID is conveniently referred to as the foot edge, while the topmost edge of each plate adjacent the edge 3l of the rear bearer 8 is referred to as the top, hook or curved edge.

It is emphasized that the invention herein is directed importantly to the manner in which these several edges have been provided with flanges, webbings, or rims, referred to as marginal flanges, etc., such that the opposite faces of any given plate are recessed or hollowed differently, each face with respect to the other,

to effectuate in their assembled relation the formation with other bars or plates the separate and distinct air passages leading alternately forward from behind the bridge toward the lire-bed between the plates or bars forming the wall (and in this sense through the bridge) and then interiorly of the bridge wall proper, so as to issue at a point remote from the forward, openings, and adjacent or at the rear bearer 8.

Thus, as a specic example, in the sectional view of Fig. 3, showing the assembly of the bars in pairs, the right-handed face of la, designated as Har, confronting the left-hand face of Ia, designated as lal, form a pair having openings along the front and rear longitudinal edges (the latter being very extensive relative to the former), but none in either the foot or hook parts; and the right-hand face of Ib, designated as lbr, confronting the left-hand face of lb, designated as lbl, form a pair having a foot opening 29 and a rearward vent 22 in the arcuate, hook, or trailing end of the bars.

For the purpose of more particularly pointing out the construction of the individual bars IB,

it will be seen from Fig. l that the bar |605 is a. generally elongated, hook-shapedplate having a generally reentrant curvature at one (rearward) end, the OD. The purpose of this curvature being in part to provide in the assembled units a OWIlg surface for the rearward movement of combustion gases moving from the fuel bed I8 over the bridge toward the combustion chamber lying immediately behin d the rear bearer 8. The opposite margin or edge- 28-29 of this plate IGa is substantially straight. and is termed for c011- venience the foot of the bar, it being adapted to engage the specially designed supporting means or bearer I0, forming part of this invention.

The opposite faces Ilia and I6b of each plate or bar have marginal flanges extending outwardly from their surfaces to form recesses therein as shown in the section view of Fig. 3, and also by the reference characters 25, 25', 25, and 28 in Figs. 1 and 2.

It should be particularly noted that the righthand face 16a, of the bar in Fig. 1 has an outward flange 28 at its foot, while the opposite face ISb of this same bar (Fig. 2) has no such flange, but has an open foot 29.

The rearward edge of the face Ilia of Fig. l has no marginal flange except along its reentrant or arcuate and uppermost edge (25'), while in contradistinction to this, the opposite face IGb of this saine bar (Fig. 2) has a marginal flange 26? along its rear, longitudinal edge. However, this' latter flanging (Fig. 2) being opened at thefoot 29, is also opened or notched to provide the vent 22, the continued part 25 of this ilanging running around again to the foot 29.

The marginal flange 25' running around the rearward edge of the face 16a. (Fig. l) is interrupted cr notched slightly to form the relatively small vent 20', and a short distance below this point the flanging 25 is graded down to form the elongated opening or vent 2D of varying width, this same ila-nging being raised again as it continues toward the foot to provide the foot llange 28 (Fig. 1).

All the bridge bars or plates I8 have a notched or indented part 30 formed adjacent the reentrant point of curvature near their upper, rearmost ends, such notched parts being adapted to engage supportably the seating edge 3| of the rear bearer plate 8.

It may be remarked here that because of the possible different quantity of air which may be required in the region of the forward vents 20 and 20 as apart from that required near the rearward vents 22, it is desirable to have separate or distinct air passages or vapertures in the main bearer l0 supplying the several diversely directed sets of channels in the bridge wall. The structure directed toward this end will be hereinafter described in greater detail.

Supporting means for the bridge bars I6 include a main bearer l0 and a rear bearer 8 (Figs. l, 2, 3) both especially designed as cooperating elements of the assembly. The main bearer l0 is an elongated plate dimensioned to extend the width of the furnace, and is cast or pressed to have for- 1 ward surface 4| depressed or stepped below the rearward surface 42, both stepped surfaces being provided with large, spaced air openings 31 and 31' of different areas, proportioned to the amount of air required to be supplied to the fuel bed in front of the bridge wall, and to the combustion chamber beyond the bridge Wall, the openings 31' in the lowermost step level or surface of said bearer Il) being dimensioned to supply air adequately to the openings 29 in the foot of the bridge assembly. The underside of the bearer I0 is provided 'with laterally extensive, depending reinforcing ribs 38, the forward end of this bearer having an upstanding, longitudinal flange 40 engageable with a seating recess 43 in the grate i4.

Each bar i6 also hasv in its foot a toe or lug 32 adapted to engage the main bearer plate I0 below the surface level of the grate i4 (Figs. 1, 2, 3) having a generally vertical surface 33 adapted to confront similarly dimensioned end flanges 44 of the bars of the grate I4, and on the-backward eX- tension a vertical surface 34 adapted to confront a vertical surface 35 formed by the step rise between the levels Il! and 42 on the main bearer I Il, by reason of which arrangement firing tools and the like used in working the re on the grate cannot unseat the bars I6.

It is to be observed that the foot of the bars le do not rest over their whole lateral width on the bearer II) but only at their front part or toe 32, the backward extension thereof being raised above the bearer plate so that where openings 29 between the bars may coincide with top flanges of the ribs 38 the air shall not be obstructed in admittance to openings 29.

'Ihe rearmost part of the main bearer l0 terminates in coextended, longitudinal mounting anges II engageable by means of bolts I3 with the ash pit closing plate I2 and the back bearer 8, respectively. If desired, the main bearer III and the back bearer 8 may be formed integrally.

The rear bearer 8 is a generally elongated plate of suitable heat resisting material having its uppermost edge 3l upset and formed suitably to engage the mounting indentures or notches 3l! of the several bridge bars. The forward side of this bearer 8 is provided with vertically extensive ribs 8 spaced apart suitably to provide reinforcement as well as means for dissipating heat from the back bearer plate 8 to prevent burning. The outward or rearward side of this back bearer 8 is provided with an extending, longitudinal flange or rib I5 (Figs. 1, 2, 4) adapted to overlie for additional security the upwardly extending flange II of the main bearer plate ID.

Reinforcing ribs I'I extend upwardly from the flange I5 to the point of inflection of the upset or inwardly turned edge SI of this bearer 8.

Operation In operation, air for combustion, entering either under natural or forced draught, rises from the ash pit below the level of the grate I4, and following the path of the tracer arrows in Figs. l and 2, moves upwardly against the main bearer plate Ill, passing through the openings 31 and t'i' therein and thence impinging upon the underside and foot portions of the bridge bars I6. From this point, the air will follow two generally distinct or separated paths one of which will be transversely through the wall, and the other by way of a substantially closed interiorly-dened channel Within the wall, depending upon which kind of bridge bar pair or combination (with respect to right and left-hand faces) it encounters.

In the path shown in Fig. l, the air enters between adjacent bars from their lower, rearward side (having no marginal flanges there) and passes through the openings 2() and 2D forward into the fuel bed I3 where it enters partly into combustion to rise and pass backwardly over the top, arcuate surface of the bridge wall assembly into the combustion chamber and thence on toward the flues.

In the path shown in Fig. 2, air enters between adjacent bridge bars I6, but only at the foot 29. This air cannot pass forward into the fuel bed I8, nor backward against the rear bearer 8 because of the confronting marginal flanges 25 and 26. The function of this portion of the air so-directed is that of combustion of the gases in the combustion chamber and serves also to prevent the excessive formation of smoke; and it is split off from the main ow of air in proportion suitable for these purposes, traversing the space between each alternate pair of bars on their ISD faces and *emerging directly into the combustion chamber by the openings 22.

It will be seen that, by means of the particular design and mounting of the bridge bars provided' by this invention, all of the air passing the bridge wall, for combustion of the fuel in front of the bridge wall, and of the gases in the combustion chamber, contacts entirely all the bars of the bridge wall assembly in passing the bridge wall, and is heated before entering the combustion areas, serving thus to promote combustion and also to keep the bars comparatively cool and prevent burningmut the bars and the rear bearer 8.

Having thus described my invention, it is pointed out that I do not wish to be restricted to any particular details of the embodiment herein set forth, but that I desire to avail myself of all the variations, modifications, combinations, and interpretations thereof which come within the scope of the appended claims, which I desire to protect by Letters Patent of the United States.

I claim:

l. Furnace bridge wall bars in the form of elongated, substantially hook-shaped plates hav ing two recessed faces with back and front longitudinally extensive edges, a hooked or curved edge, and a foot edge, the recesses in said faces being formed by outwardly7 extensive anges, the flange of one face beginning at the said hooked edge and running around to and along the said front longitudinal edge and around said foot edge terminating at said rear longitudinal edge, the front longitudinal flange being graduated in wardly as it approaches the said foot edge, the other face of said plate having a flange running entirely around said plate but opened or interrupted at said foot end and near said hook end.

2. A bridge wall asembly for furnaces comprising bridge bars in the form of elongated, substantially hook-shaped plates having two recessed faces with back and front longitudinally extensive edges, a hooked or curved edge, and a foot edge, the recesses in said faces being formed by outwardly extensive flanges, the flange of one face beginning at the said hooked edge and running around to and along the said front longitudinal edge and around said foot edge terminating at said rear longitudinal edge, the front longitudinal flange being graduated inwardly as it approaches the said foot edge, the other face of said plate having a flange; running entirely around said plate but opened or interrupted at said foot end and near said hook end, and mounting bearers including a main bearer plate having relatively stepped levels with air passages therein, a `grate-engaging flange along the edge of one step level, and a back bearer extended angularly respective to said main bearer and adapted to engage supportably the hooked poru tion of said bridge bars.

3. A furnace bridge wall assembly comprising bridge bars in the form of elongated plates having two recessed faces with back and front longitudinally extensive edges, a foot and a top edge, the recesses in said faces being formed by flanging or ribbing running substantially around the edges of said plates the flanging of one face beginning at the said top edge and running around said foot edge to terminate at or near said rear longitudinal edge, the front longitudinal flange being graded down as it approaches the said foot edge, the other face of said plate having a flange running entirely around said plate but opened or interrupted at said foot end and near said top end, and mounting members including a wide plate having apertured, stepped surfaces.

4. Furnace bridge wall members in the form of substantially flat, elongated, unitary plates having two opposite faces, one of which is provided with ribbing which runs around the edge of the plate and which is opened at the opposite longitudinal extremities thereof, and the other face of which is provided with ribbing which runs along the edge of the plate across both longitudinal extremities and one lateral extremity, the ribbing along the last-mentioned lateral extremity having parts cut away to provide a passage for air through said part of the ribbing.

5. Furnace bridge wall members in the form of -narrow plates having two recessed faces with back, front, foot and top edge extremities, the recess in one said face being defined by raised portions along the said foot, front, and top edge extremities thereof with the raised portions along the said front edge having portions cut away, and the recess in the other said face being defined by raised portions along the said front, back, and top edge extremities thereof with a portion cut away near the said top edge part thereof, the said plates being adapted for assembly in side by side relation with correspondingly disposed raised portions of adjacent faces in confronting relation and with their respective confronting recessed parts forming between one pair of adjacent plates a passage for air leading from the foot to the top edge extremities of the said pair of plates, and forming between a plate of the said first mentioned pair and another said plate adjacent the said pair a second pair of plates said face being formed by raised portions runningl 10 along the said bottom, front, and top extremities with portions cut away in the raised portion along the said front extremity, and the said channel in the opposite face being formed by raised portions running along the said front, top, and rear extremities thereof with portions of the said raised part cut away near the said top extremity of said face.

7. Furnace bridge wall bars for use with a bearer and a grate partly supported by said Y bearer, said bars comprising unitary plates having two faces with front, rear, foot, and top edge parts and webbing running along the said foot, front, and top edge parts of one said face and having portions along the front edge part graded inwardly toward said face, and the opposite face of the plate having webbing running along the front, top, and rear edge parts thereof and having a portion of said webbing cut away at the top edge part thereof, said plates also hav ing an edgewise surface which lits flush against an extremity of a said grate when the said bridge bar plates are in assembled relation with the bearer and grate to form a bridge wall.

ALEXANDER HYND. 

